The Vatican flag in front of the Brandenburg gate in Berlin before the pope's visit this week. Photograph: Kay Nietfeld/EPA

A hundred MPs in Germany are planning to boycott a speech given in the German parliament by the pope on his first official visit to his homeland.

MPs from the Green, Left and Social Democratic (SPD) opposition parties have indicated they will stay away from the Bundestag during the Bavarian-born pontiff's address on Thursday afternoon.

"A head of state who disregards labour rights, women's rights and the right to sexual self-determination should not be allowed to address the Bundestag," Ulla Burchardt, an SPD politician from Dortmund, told Der Spiegel.

Others take umbrage at the decision to classify the pope as a head of state rather than the head of a religion, qualifying him for the honour of addressing parliament. Rolf Schwanitz, also SPD, who used to be a minister of state under Gerhard Schröder, said it set a dangerous precedent.

"Never before has a religious leader spoken in the German Bundestag – and for good reason, both then and now. The constitution, in respect of religion and world view, obliges the state to remain neutral," wrote Schwanitz in a Wednesday's FT Deutschland.

Alexander Süssmair of the socialist Left party told Der Spiegel he "cannot even imagine what the democratic Federal Republic of Germany could learn from the representative of an absolute monarchy".

With one sixth of Germany's politicians expected to stay away, former Bundestag members have been invited to fill the empty seats.

The parliamentary boycott is not the only awkward situation Benedict XVI will encounter in Berlin. His meet-and-greets on Thursday include the chancellor, Angela Merkel (a Lutheran), the gay mayor of Berlin, Klaus Wowereit, and Christian Wulff, the Roman Catholic president who is on his second marriage after a divorce.

Wowereit has angered LGBT groups by saying he welcomes the pontiff's visit to the capital.

"We are against discrimination, unequal treatment, against the banning of condoms and we want to make that clear," Joerg Steinert, director of the German Gay and Lesbian Association told Associated Press Television News. "We will be visible when the pope addresses parliament."

The breadth of potential social and religious conflicts represented by the German leadership reflects the state of a nation that is proud of, but also sometimes indifferent and antagonistic towards, the German-born pontiff and the church he represents.

In a weekend address on German television before his visit from 22 to 25 September, Benedict told viewers he was especially excited to visit Berlin and speak in the German parliament.

"All of this is not religious tourism, even less a show," the 84-year-old pope, born Joseph Ratzinger, said in an address broadcast on ARD television late on Sunday. "It is about bringing God back into our field of view; God who is often missing, but so very needed."

A recent poll indicated most Germans did not think the papal visit was particularly important. Only 14% of 1,008 Germans surveyed by the Forsa institute earlier this month said the visit was of personal importance to them, compared with 55% that said it held "no importance whatsoever".

Criticism of the pope is often highest among members of his own flock. A record 181,000 left the Catholic church last year in protest against its sexual abuse scandals and increasingly conservative line. For the first time, that was more than those quitting German Protestant congregations and topped the total number of new baptisms into the Catholic church.